Would love to know the answer to this! Ive stocked up on plenty of smalls, which we will obv eventually have to swap for mediums... but i wonder when?!
I have a feeling ppl are going to say that it depends on the size & shape of the individual baby tho! As this is my 1st, i have no idea at what age they generally reach the different weights/lengths! So all the websites that say "fit up to 15lb" etc are totally lost on me!
Sorry im no help!
xxx